Externally threaded jewelry is where the threads are actually on the outside of the metal shaft. The balls have the threaded hole that is screwed onto the shaft.

The wearable area is 5/8". Each nipple stirrup comes with a 14g, 1" barbell with 5mm balls.

In our drop-down menus for adding to cart, we show the gauge of the item you are ordering, then the length/diameter, then the ball size if it has any:

Jewelry is measured through a gauge system (see chart below). The higher the gauge number the smaller the wire is. A standard "earring" is usually 20 gauge. Jewelry gauges/sizes can vary between manufacturers. There is no universal regulation on companies to make a standard size in body jewelry. A big part of this is that some jewelry is made overseas and measured in millimeters. And in the USA jewelry is measured in inches/gauges. So many times jewelry can be anywhere from .5mm to 1mm different.